Best US TV Show Cancelled Too Soon

What's the best US TV show cancelled before it had time to tell its story?

Or the worst, in which case it was undoubtedly a good idea to put it out of its misery.

My own favourite was Dark Skies. I also regret the passing of Odyssey 5 and Poltergeist: The Legacy. I think The Lost World and Sliders might have had another series in them as well.

There are two more, but I can't remember their names. One was about aliens who infiltrated human bodies and changed them so they could breathe underwater. The other featured a teenage girl washed up on a beach who turned out to be the daughter of Satan.

Anything to interrupt the never-ending flow of TCIC blogs.